A federal jury ruled that Monsanto was liable for a California man’s cancer and ordered the Roundup manufacturer to pay $80m in damages.

The ruling on Wednesday, which holds the company responsible for the cancer risks of its popular weedkiller, is the first of its kind in US federal court and a major blow to Monsanto and its parent company, Bayer. A representative said Bayer would appeal.

In a verdict during an earlier phase of the trial, the jury in San Francisco unanimously ruled that the herbicide was a “substantial factor” in causing the cancer of Edwin Hardeman.